Peter Tremayne is the pen name of British historian and novelist Peter Berresford Ellis, a specialist in Celtic and Irish history. Born in Coventry in 1943, he began publishing fiction under the Tremayne name in the 1970s, initially writing fantasy, supernatural fiction and historical adventure. His scholarly knowledge of early Irish society, religious history and Brehon law later became the foundation for his best-known historical mysteries.
Tremayne is chiefly known for the long-running Sister Fidelma Mysteries, beginning with Absolution by Murder. Set mainly in seventh-century Ireland, the series follows Fidelma of Cashel, a religious sister and qualified advocate who investigates murder alongside the Saxon monk Brother Eadulf. The novels combine criminal investigations with political intrigue, legal disputes and conflicts between Celtic and Roman Christian traditions, creating a detailed portrait of early medieval Ireland and its neighbouring kingdoms.